The Effect of X Rays on Single Colonies of Pandorina

Abstract

(1) The green alga Pandorina is a suitable object for the study of the radiation effects on single colonies and their offspring. (2) In colonies of the same clone the doses required for immediate and delayed death are sharply limited for each type of reaction. (3) In colonies of wild cultures the lethal doses vary over a larger range. This difference is proof of the significance of the biological factor. (4) Delayed death always occurs exactly at the time of division independent of the stage of development when irradiated. (5) Normal cell division is associated with the loss of the effect of previous irradiations. (6) In Pandorina recovery from irradiation effects was not observed. (7) The proportion of the doses required for delayed, death and for immediate death in Pandorina is 1 : 100.